Why Do Some People Need Blood Thinners?

A person may be required to take blood thinners if they have insufficient blood flow to the brain or if they suffer from some form of blood vessel or heart disease, according to National Institutes of Health's MedlinePlus. People who have recently undergone heart valve surgery, have congenital heart defects or who have an abnormal heart rhythm may also be required to take blood thinners.

Blood thinners reduce the buildup of blood clots in the veins and arteries, which results in a person having a smaller chance of suffering from a stroke or heart attack, according to MedlinePlus. The two main types of blood thinners that are prescribed to people and that can be bought without a prescription are antiplatelets and anticoagulants.